Support for sprintmodel.f input

Lex supports ! for comment, and in col 6

Parser has support for extra syntaxes used in psinring model
- end subroutine name
- variable called "If"
changes to optimize to support new parsing

add psinringin model .f example to project
include in test cases

v0.9.5: Include underscores in NAME definition. add test case for var name wi…

fix unerscores in var names issue

v0.9.4

Fix consistent expression formatting after user feedback

v0.9.3

Update README.md

v0.9.2

Update ci.yml